1. Field of the Invention
The Present invention relates to an ink jet recording apparatus for effecting recording by using recording means for discharging plural different color inks.
2. Related Background Art
A recording apparatus having a function such as a printer function, a copier function, a facsimile function and the like, a composite electronic equipment or work station including a computer, a word processor and the like, and a recording apparatus used as an output device of an industrial recording apparatus compositely combined with various types of processing equipments are designed so that an image (including a character and/or a symbol) is recorded (or printed) on a recording medium (recording material) such as a paper, cloth, a plastic sheet, an OHP sheet or the like on the basis of recording information. Such recording apparatuses can be grouped into an ink jet type, a wire dot type, a thermal type, a laser beam type and the like in dependence upon a recording system.
In a recording apparatus of serial type in which the recording is effected while performing main scanning along a direction transverse to a conveying direction (paper feeding direction or sub-scanning direction) of a recording medium, an image is recorded by a recording head (as recording means) mounted on a carriage shifted (main-scanned) along the recording medium. In the apparatus, by repeating such an operation that a predetermined amount of sheet feeding (pitch conveyance as sub-scanning) is effected after one-line recording is finished, and then a next line image is recorded (main scanning) on the recording medium which is now stopped, the recording is performed with respect to the entire recording medium. On the other hand, in a recording apparatus of line type in which the recording is effected only by the sub-scanning in the conveying direction of the recording medium (recording material), the recording medium is set at a predetermined recording position, and, by repeating such an operation that a predetermined amount of sheet feeding (pitch feeding) is effected after one-line recording is performed collectively and then next one-line recording is performed collectively, the recording is performed with respect to the entire recording medium.
Among such recording apparatuses, a recording apparatus of ink jet type (ink jet recording apparatus) performs the recording by discharging ink from a recording head as recording means toward a recording medium. The ink jet recording apparatus has the following advantages. That is to say, the recording means can easily be made compact, a highly fine image can be recorded at a high speed, an image can be recorded on a plain paper without special treatment, and a running cost is low. Further, since the apparatus is of non-impact type, noise is small, and a color image can easily be recorded by using plural color inks. Further, according to an ink jet recording apparatus of line type using a recording head of line type in which a large number of discharge ports are disposed along a width-wise direction of the recording paper, the recording can be effected at a higher speed.
Particularly, in recording means (recording head) of ink jet type for discharging ink by utilizing thermal energy, since high density arrangement of liquid paths (discharge port arrangement or nozzle arrangement) can be realized by means of electrical/thermal converters, electrodes and liquid path walls and a top plate formed on a substrate by a semiconductor manufacturing process such as etching, deposition and/or spattering, further compactness can be achieved. Further, in the ink jet recording apparatus, there have been various requests for the material quality of the recording medium (recording material), and, in recent years, development for such request has been progressed, and, thus, cloth, leather, non-woven fabric, metal and the like has been used as the recording medium, as well as normal recording media such as paper (including a thin paper and a processed or converted paper) and a plastic thin board (OHP and others).
In the ink jet recording apparatus, the image is recorded on the recording medium by discharging the ink from a discharge port in response to an electrical signal. In some cases, due to penetration of air into the discharge port or increase in viscosity of the ink by drying, the ink droplet may not be discharged from the discharge port in response to the electrical signal. As one of methods for restoring a normal discharging condition from such ink non-discharging condition (including a poor discharging condition), there is a method (suction recovery means) in which ink not contributing to the image recording is sucked and discharged from the discharge port. In such suction recovery means, in many cases, as one of means (pressure generating devices) for generating ink sucking negative pressure, a tube pump in which a negative pressure is generated in a pump tube by rotating a pump roller while urging the pump roller against the pump tube, i.e., by squeezing the pump tube, has been used. As suction recovery means, for example, there is an arrangement in which a suction hole is formed in a cap capable of capping the recording head and the tube pump is connected to the suction hole.
In some cases, the cap and the tube pump are designed to be driven cooperatively in accordance with a rotational direction of a driving source (for example, a purge motor) of a recovery unit. That is to say, first of all, the cap is urged against an ink discharge port forming face (discharge port face) of the recording head by a normal rotation of the purge motor, thereby capping the recording head. Then, the tube pump is driven reversely by a reverse rotation of the purge motor. When driven reversely, in the tube pump, the pump roller is rotated while being urged against the pump tube to squeeze the pump tube, thereby generating the negative pressure. The negative pressure is introduced into the cap through the suction hole. In this case, since the recording head is capped by the cap, the viscosity increased ink and/or bubbles unsuitable for the recording are sucked from the discharge ports of the recording head by the negative pressure introduced into the cap, and the different color inks flow toward the single suction hole of the cap through a cap absorbing body provided upwardly, thereby discharging the inks forcibly. Thereafter, by rotating the purge motor in the normal direction, the cap is separated from the ink discharge port forming face of the recording head to thereby release the capping. In this way, the suction recovery operation is completed.
However, in the recovery unit used in the conventional ink discharge recovery device including the above-mentioned arrangement, there is the following technical problem to be solved. That is to say, due to recent colorization, high image quality and high resolution, since the number of ink discharge ports has been increased, the number of ink colors has been increased and a size of the discharged ink droplet has been decreased, the handling of the recording head becomes more delicate. Thus, there is caused such trouble that different color inks enter into different color discharge ports to cause mixing of color (color mixing) in recording, with the result that a correct color recorded image cannot be obtained. This trouble frequently occurs in the suction recording operation. To cope with this, although a technique in which respective color discharge ports (or nozzles) are sucked by respective suction caps or a technique in which respective color discharge ports are successively sucked by a single cap, can be considered, such techniques make the mechanism more complicated and more bulky, and increase the cost and increase the suction recovery time. Further, in the technique in which the suction is effected by using the single cap, there is an apparatus having the technique in which, from after the suction recovery to immediately before the recording (printing), by discharging and discarding the ink in the vicinity of the discharge ports of the recording head, the inks in the respective color discharge ports (respective color nozzles) are made pure and then the recording is started. Also in this apparatus, as the number of discharge ports (nozzles) is increased, an amount of ink to be discarded tends to increase, and, thus, there still remains a technical problem (to be solved) that consumption of ink is hastened.
An object of the present invention is to provide an ink jet recording apparatus which can prevent different ink from entering into different discharge port even when plural different inks are sucked by using a single cap and which can recover a normal image recording condition of recording means having no color mixing with a simple and cheap construction and with a short time pre-ejection operation having low consumption of ink, and can prevent ink contamination within the apparatus by reducing generation of ink mist caused by the pre-ejection.
Another object of the present invention is to provide an ink jet recording apparatus for effecting recording by using recording means for discharging plural different inks, which comprises a cap for covering a plurality of discharge ports for discharging the different inks and a pump connected to a suction hole of the cap and adapted to generate negative pressure within the cap, and in which the discharge ports and the suction hole are arranged so that an ink flow path from the discharge ports to the suction hole when the inks are sucked from the discharge ports by operating the pump are not passed through the different ink discharge ports.